On May 26, 2021, Dimitrios M. Thilikos from LIRMM, CNRS gave an online talk at the Virtual Discrete Math Colloquium about an upper bound of the size of obstructions for minor-closed classes of graphs at the Virtual Discrete Math Colloquium. The title of the talk was “Bounding Obstructions sets: the cases of apices of minor closed classes“.

## Ben Lund gave a talk on the existence of a limit shape for lattice zonotopes at the Discrete Math Seminar

On May 25, 2021, Ben Lund from the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on the existence of a limit shape for lattice zonotopes in all dimensions and other relevant results. The title of his talk was “Limit shape of lattice Zonotopes”.

## Benjamin Bumpus gave an online talk introducing directed branch-width for directed graphs at the Virtual Discrete Math Colloquium

On May 21, 2021, Benjamin Bumpus from the University of Glasgow gave an online talk at the Virtual Discrete Math Colloquium about the directed branch-width for directed graphs. The title of his talk was “Directed branch-width: A directed analogue of tree-width“.

## Pascal Gollin gave a talk on extending a vertex-flame to a large vertex-flame in a countable digraph at the Discrete Math Seminar

On May 18, 2021, Pascal Gollin from the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on the existence of a large flame extending a given vertex-flame in a countable digraph. The title of his talk was “Enlarging vertex-flames in countable digraphs“.

## Johannes Carmesin gave an online talk on locally planar embeddability of graphs on a surface at the Virtual Discrete Math Colloquium

On May 12, 2021, Johannes Carmesin from the University of Birmingham gave an online talk at the Virtual Discrete Math Colloquium on the analogue of Whitney’s theorem for the locally planar embedding of graphs on a surface. The title of his talk was “A Whitney type theorem for surfaces: characterising graphs with locally planar embeddings“.

## Mark Siggers gave a talk on the complexity of the list switch homomorphism problem for signed graphs at the Discrete Math Seminar

On May 11, 2021, Mark Siggers from the Kyungpook National University gave a talk at the Discrete Math Seminar about the complexity of deciding whether there is a list homomorphism from a signed graph G to another signed graph switching equivalent to H. The title of his talk was “The list switch homomorphism problem for signed graphs“.

## Raul Lopes gave an online talk on the FPT algorithm for finding the cylindrical grid in a directed graph of large directed tree-width at the Virtual Discrete Math Colloquium

On May 6, 2021, Raul Lopes from Universidade Federal do Ceará gave an online talk at the Virtual Discrete Math Colloquium providing a fixed-parameter tractable algorithm to find a large cylindrical grid as a butterfly minor in a directed graph of large directed tree-width. The title of his talk was “Adapting the Directed Grid Theorem into an FPT Algorithm“.